Materials, which may, via suitable temperature excursions, be reversibly switched between two structural phases characterized by different resistivities have the potential to be employed as phase change memory materials. One class of materials having such properties is materials that comprise germanium (Ge) and antimony (Sb). The materials including Ge and Sb are hereinafter referred to as GeSb materials.
In order to fabricate practical memory devices, it will be necessary to deposit such materials upon substrates of substantial topographic complexity. A possible structure for implementing a phase change memory device is a line-and-via structure similar to those found in interconnect wiring structures. In such structures, the phase change material in the narrow via would constitute the active element of the device.
Chemical vapor deposition (CVD) is a promising potential method to deposit GeSb materials. It has been found that the addition of small amounts (on the order of about 10 atomic percent or less) of dopant atoms, such as nitrogen, is a useful technique for modifying the resistivity of these films.
While CVD processes often exhibit desirable conformality, CVD processes frequently are performed at temperatures substantially exceeding 400° C. Such a high deposition temperature severely restricts the choice of materials which may be included in an integrated device. Therefore, CVD processes which are operable substantially below 400° C. are desired.
Low temperature CVD processes are even more desirable for materials comprising at least two different elements selected from Groups IVB, VB, and VIB of the Periodic Table of Elements (IUPAC nomenclature) since several elements such as, for example, antimony (Sb), arsenic (Ar), tellurium (Te), selenium (Se), phosphorus (P) and sulfur (S), exhibit vapor pressure approaching or exceeding 1 mtorr at temperatures as low as 500° C.
Any deposition process for materials including the above-mentioned elements from Groups IVB, VB, and VIB of the Periodic Table of Elements, such as GeSb, would have to compete with a substantial evaporation rate.
In view of the above, there is a need for providing a low temperature (less than 400° C.) CVD process in which nitrogen atoms can be incorporated into a material that comprises germanium (Ge) and antimony (Sb).